What is the most appropriate next treatment for a hypothermic patient with confusion, hypotension, bradycardia, and hypoxia, who has been initiated on passive rewarming by Emergency Medical Services (EMS)?

Active Truncal Rewarming is the Most Appropriate Next Treatment

For this patient with moderate hypothermia (32°C) presenting with altered mental status, hypotension, and bradycardia, active truncal rewarming should be initiated immediately following passive rewarming by EMS.

Rationale Based on Severity Classification

This patient has moderate hypothermia (28-32°C) based on the core temperature of 32.0°C, with concerning signs including confusion, hypotension (BP 95/70), bradycardia (P 60), and bradypnea (R 10). 1, 2

• The American Heart Association classifies hypothermia at 32°C as moderate, requiring escalation beyond passive rewarming measures. 1, 2
• Passive rewarming alone is inadequate for moderate hypothermia and may actually cause temperature decrease during transport, as demonstrated in trauma studies. 1
• Active external rewarming is specifically recommended for patients with moderate hypothermia, particularly when hemodynamically unstable. 1, 2

Why Active Truncal (External) Rewarming is Correct

Active external rewarming methods include forced warm air blankets, heating pads, radiant warmers, and chemical heat blankets applied to the trunk and extremities. 1, 2

• For moderate hypothermia with stable (though borderline) hemodynamics, active external rewarming combined with warmed intravenous fluids and humidified oxygen is the appropriate next step. 1, 2
• Studies demonstrate that active resistive heating during transport increases core temperature by +0.8°C versus -0.4°C with passive measures alone. 1
• Even in severe hypothermia (<30°C), forced-air warmers have successfully rewarmed patients to >35°C, demonstrating efficacy despite peripheral vasoconstriction. 1

Why Other Options Are Inappropriate at This Stage

Cardiopulmonary bypass (Option B) and heated peritoneal lavage (Option D) are reserved for severe hypothermia with cardiovascular collapse or cardiac arrest:

• These invasive active core rewarming methods are indicated for patients with core temperatures <28°C or those in cardiac arrest. 1, 3
• This patient has a pulse and blood pressure, making these aggressive interventions premature and unnecessarily risky. 3
• Survival rates with extracorporeal circulation are only 13% in cardiac arrest patients, compared to 100% with less invasive methods in hemodynamically stable patients. 3

Endovascular warming devices (Option C) are not first-line therapy:

• While endovascular devices can provide active core rewarming, they are not standard initial management for moderate hypothermia with stable vital signs. 4
• These devices are typically reserved for severe cases or when other methods fail. 4

Clinical Algorithm for This Patient

1. Continue passive rewarming already initiated by EMS (remove wet clothing, insulate from environment, cover head/neck). 1, 2

2. Immediately add active external rewarming with forced warm air blankets, heating pads, or chemical heat blankets to trunk and extremities. 1, 2

3. Administer warmed intravenous fluids and provide humidified, warmed oxygen via advanced airway if needed. 1, 2

4. Monitor core temperature every 5-15 minutes and watch for complications including arrhythmias, rewarming shock, and burns from heating devices. 2

5. Target rewarming to 36°C minimum, ceasing at 37°C as higher temperatures are associated with poor outcomes. 2

6. Escalate to active core rewarming (peritoneal lavage, extracorporeal methods) only if hemodynamics deteriorate or cardiac arrest occurs. 1, 3

Critical Pitfalls to Avoid

• Do not delay active rewarming waiting for the patient to passively rewarm, as this is ineffective in moderate hypothermia. 1
• Handle the patient gently during all interventions to avoid triggering ventricular arrhythmias. 1, 2
• Place insulation between heat sources and skin and monitor frequently for burns, as active rewarming devices can cause thermal injury. 1, 2
• Do not jump to invasive core rewarming methods in a patient with perfusing rhythm and measurable blood pressure. 3